The present invention relates to a thin film circuit board device having passive elements in wiring layers and a method for manufacturing the same.
Various kinds of information such as music, audio data, images or the like can be readily treated by compact information processors such as personal computers or mobile computers with the digitization of data. The band of these information has been compressed by an audio codec technique or an image codec technique. Thus, an environment in which the information is easily and efficiently distributed to various kinds of communication terminal equipment by a digital communication or a digital broadcasting has been arranged. For instance, audio data and video data (refer them to as AV data, hereinafter) may be received outdoors by portable telephones.
The transmitting and receiving system of data or the like has been conveniently utilized in small areas as well as in homes in various ways by forming preferable network systems. As the network systems, for instance, a narrow band radio communication system of a band of 5 GHz which is proposed in IEEE 802.11a, a radio LAN system of a band of 2.45 GHz which is proposed in IEEE 802.11b or a short-range radio communication system called a Bluetooth has been paid attention to.
In the transmitting and receiving systems for data, such wireless network systems may be effectively utilized to easily deliver various kinds of data in different places such as homes or outdoors without using repeaters, access to various types of communication networks, or transmit and receive data.
It is essentially necessary for the transmitting and receiving systems to realize compact, light and portable communication terminal equipment having the above-described communication function. The communication terminal equipment needs to modulate and demodulate an analog high frequency signal in a transmitting and receiving part. Accordingly, the communication terminal equipment generally has a high frequency transmitting and receiving circuit based on a super-heterodyne system in which a transmitted and received signal is temporarily converted into an intermediate frequency signal.
A high frequency transmitting and receiving circuit 100 comprises, as shown in FIG. 1, an antenna part 101 having an antenna or a change-over switch to receive or transmit an information signal, and a transmission and reception switching unit 102 for switching transmission and reception. The high frequency transmitting and receiving circuit 100 is provided with a receiving circuit part 105 including a frequency converting circuit part 103, a demodulating circuit part 104 or the like. Further, the high frequency transmitting and receiving circuit 100 is provided with a transmitting circuit part 109 including a power amplifier 106, a drive amplifier 107, a modulating circuit part 108 or the like. Further, the high frequency transmitting and receiving circuit 100 includes a reference frequency generating circuit part for supplying a reference frequency to the receiving circuit part 105 or the transmitting circuit part 109.
The high frequency transmitting and receiving circuit 100 having the above-described structure, the detail of which is omitted, includes large functional parts such as various filters respectively inserted between stages, VCO (voltage controlled oscillator), SAW filters (surface acoustic wave filter), etc. The high frequency transmitting and receiving circuit 100 further includes many passive parts such as inductors, resistors, capacitors characteristic of high frequency analog circuits such as matching circuits or bias circuits. Therefore, the high frequency transmitting and receiving circuit 100 becomes large as a whole, so that the communication terminal equipment using this circuit 100 hardly becomes compact and light.
In the communication terminal equipment, as shown in FIG. 2, a high frequency transmitting and receiving circuit 110 based on a direct conversion system is used in which an information signal is transmitted and received without converting the information signal into an intermediate frequency. In the high frequency transmitting and receiving circuit 110, the information signal received by an antenna part 111 is supplied to a demodulating circuit part 113 through a transmission and reception switching unit 112 and a base-band process is directly carried out. In the high frequency transmitting and receiving circuit 110, the information signal generated in a source is not converted into an intermediate frequency in a modulating circuit part 114 and directly modulated into a prescribed frequency band. The modulated signal is transmitted from the antenna part 111 through an amplifier 115 and the transmission and reception switching unit 112.
The above-described high frequency transmitting and receiving circuit 110 does not convert the information signal into the intermediate frequency and carries out a direct detection to transmit and receive the information signal. Therefore, the number of parts such as filters is reduced and an entire construction is simplified and a configuration substantially composed of one chip may be realized. However, the high frequency transmitting and receiving circuit 110 needs a filter or a matching circuit disposed in a post-stage. Since the high frequency transmitting and receiving circuit 110 carries out an amplifying operation once in a high frequency stage, the circuit 100 hardly obtains an adequate gain. A base-band part also needs to carry out an amplifying operation. Accordingly, the high frequency transmitting and receiving circuit 110 needs a cancellation circuit with DC offset or an excess low-pass filter, so that entirely consumed power is increased.
The conventional high frequency transmitting and receiving circuits of both the super-heterodyne system and the direct conversion system, as mentioned above, cannot obtain adequate characteristics as the transmitting and receiving circuits, in addition to the miniaturization and light-weight of the communication terminal equipment. Therefore, in the high frequency transmitting and receiving circuit, various attempts for modularizing, for instance, an Si-CMOS circuit as a base to be compact with a simple structure have been carried out. That is, as one of them, there exists a method for manufacturing what is called, a one-chip circuit board device. In this method, for instance, passive elements having good characteristics are formed on an Si substrate and a filter circuit or a resonator or the like are formed on an LSI, and further, the logic LSI of the base-band part is integrated.
It is important for the above-described one-chip circuit board device how to form the passive elements having good performance on the LSI. In an inductor 120 shown in FIGS. 3A and 3B, a large recessed part 124 corresponding to an Si substrate 121 and an inductor forming part 123 of an SiO2 insulating layer 122 is formed. The inductor 120 is provided with a coil part 127 so as to close the opening part of the recessed part 124. The coil part 127 is connected to a first wiring layer 125 so as to protrude into the recessed part 124 and connected to a second wiring layer 126 extended on the insulating layer 122. In the inductor 120 constructed as described above, a forming step is complicated, so that the forming steps are increased to increase a manufacture cost.
In the conventional circuit board device, the electrical interference of the Si substrate provided between a circuit part of an analog circuit and a base-band circuit part of a digital circuit constitutes a serious problem.
As circuit board devices that overcome the above-described problems, for instance, a circuit board device 130 using an Si substrate as a base substrate as shown in FIG. 4 has been proposed. Further, a circuit board device 140 using a glass substrate as a base substrate as shown in FIG. 5 has been proposed.
In the circuit board device 130 shown in FIG. 4, after an SiO2 layer 132 is formed on an Si substrate 131, a circuit part 133 is formed by a lithography technique. In the circuit part 133, the detail of which is omitted, passive elements 136 such as, for instance, inductors, resistors, capacitors, etc. are formed on a lower electrode 135 together with a pattern wiring 134 in multi-layers by a thin film forming technique or a thick film forming technique. The lower electrode 135 functions as a contact terminal so that these passive elements 136 are electrically connected to the pattern wiring 134.
In the circuit board device 130, terminal parts connected to the inner pattern wiring 134 through vias as through holes for relay are formed on the circuit part 133. Circuit elements 137 such as a high frequency IC, an LSI, etc. are directly mounted on these terminal parts by a flip chip mounting method. The circuit board device 130 is mounted on, for instance, a mother board, so that a circuit part and a base-band circuit part can be divided to suppress the electrical interference of both the circuit parts.
In the circuit board device 130 shown in FIG. 4, the Si substrate 131 having an electric conductivity functions upon forming respectively the passive elements in the circuit part 133. However, this substrate undesirably constitutes a factor of interference upon realizing the good high frequency characteristics of the respective passive elements.
On the other hand, the circuit board device 140 shown in FIG. 5 uses a glass substrate 141 as a base substrate in order to solve the problems of the Si substrate 131 forming the circuit board device 130 shown in FIG. 4. In the circuit board device 140, a circuit part 142 is formed on the glass substrate 141 by the lithography technique. In the circuit part 142, the detail of which is omitted, a lower electrode 144, and passive elements 145, for instance, inductors, resistors, capacitors, etc. are formed together with a pattern wiring 143 in multi-layers by the thin film forming technique or the thick film forming technique.
In the circuit board device 140 shown in FIG. 5, terminal parts connected to the inner pattern wiring through vias or the like are formed on the circuit part 142. Circuit elements 146 such as a high frequency IC, LSI, etc. are directly mounted on these terminal parts by a flip chip mounting method. In this circuit board device 140, the glass substrate 141 having no electric conductivity is used to suppress a capacity coupling between the glass substrate 141 and the circuit part 142. Thus, the passive elements having good high frequency characteristics can be formed in the circuit part 142.
In the above-described circuit board devices 130 and 140, a pattern of a high frequency signal system is formed through a wiring layer formed on the above-described Si substrate 131 or the glass substrate 141. Further, a supply wiring for a power source or a ground, a signal wiring for a control system, etc. are formed through the wiring layer. Therefore, in these circuit board devices 130 and 140, an electrical interference is generated respectively between the wiring. Further, since the wiring layers are formed in multi-layers, a manufacture cost is increased. The wiring patterns are pulled around to cause the devices themselves to be enlarged.
In the circuit board device 130, a package 150 is formed to be mounted on an interposer board 151 as shown in FIG. 6. The package 150 serves to mount the circuit board device 130 on one surface of the interposer board 151 and is entirely encapsulated with an insulating resin 152. In the package 150, pattern wiring 153 or input and output terminal parts 154 are respectively formed on both the front and back surfaces of the interposer board 151. Further, many electrode parts 155 are formed in the periphery of an area on which the circuit board device 130 is mounted.
In the package 150, while the circuit board device 130 is mounted on the interposer board 151, the circuit board device 130 is electrically connected to the electrode parts 155 by wires 156 in accordance with a wire bonding method. Thus, power can be supplied from an external power source to transmit a signal to and receive a signal from an external circuit. Consequently, in the circuit board device 130 shown in FIG. 4, electrodes 138 to which the pattern wiring 134 or the wires 156 are connected are formed on a surface layer on which the circuit elements 137 such as the high frequency IC, LSI, etc. are mounted. The circuit board device 140 shown in FIG. 5 is packaged in the same manner as described above.
These circuit board devices 130 and 140 are mounted on the interposer board 151 and packaged as mentioned above, however, the thickness or the area of the package 150 is inconveniently increased. Both the circuit board devices 130 and 140 increase the cost of the package 150.
A shield cover 157 with which the circuit elements 137 such as the high frequency IC, LSI, etc. mounted on the circuit board devices 130 and 140 are covered to reduce the influence of electromagnetic wave noise is attached to the package 150. Therefore, in the package 150, heat generated from the circuit elements 137 or the like is stored in the shield cover 157 to deteriorate characteristics as the transmitting and receiving circuit, so that a heat radiating mechanism needs to be provided.
In such a package 150, since the Si substrate 131 or the glass substrate 141 is used in the circuit board devices 130 and 140, it is difficult to provide heat radiating mechanisms for radiating heat from the substrate sides to cause the devices themselves to be enlarged.
Since the relatively expensive Si substrate 131 or the glass substrate 141 is used as the base substrate to increase the cost of the circuit board devices 130 and 140, the circuit board devices 130 and 140 are hardly provided at low cost.
In the circuit board devices 130 and 140, the pattern wiring 134 and 143 are patterned and formed in the circuit parts 133 and 142. In this case, there is a fear that, for instance, etching liquid used in an etching process may possibly corrode the lower electrodes 135 and 144 or the passive elements 136 and 145 or the like. Accordingly, in the circuit board devices 130 and 140, there is also a fear that the passive elements 136 and 145 may be possibly deteriorated, or an inconvenience may be possibly generated in an electric contact between the passive elements 136 and 145 and the pattern wiring 134 and 143.